CBSE - X - Biology - How Do Organisms Reproduce?
how is parthenogenisis possible??
Parthenogenesis is a particular form of asexual reproduction in which females produce eggs that develop without fertilization. Parthenogenesis is seen to occur naturally in aphids, daphnia, rotifers, and some other invertebrates.
The offspring of parthenogenesis will be all female if two like chromosomes determine the female sex, but they will be male if two like chromosomes determine the male sex, because the process involves the inheritance and subsequent duplication of only a single sex chromosome. The offspring may be capable of sexual reproduction, if this mode exists in the species. In many cases, parthenogenesis occurs when one gender (typically the male) is unavailable in the general vicinity. Once males are again available, the parthenogenesis-created females would be capable of mating with the males and creating normal offspring.
In parthenogenesis, the offspring originates from the genetic material contained within an egg cell.
Since there are so many variables in parthenogenesis, there is little that can be said for sure unless the specific methods of the particular parthenogenetic tendencies of an organism are known. Even external factors can trigger parthenopcarpy. For example - Parasitic bacteria like Wolbachia have been noted to nduce parthenocarpy in many insect species with haplodiploid systems. They also cause gamete duplication in unfertilized eggs causing them to develop into female offspring.
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